The present invention is directed to improvement of so-called collector type writing instruments, such as ball-point pens, felt tip pens, markers, fountain pens, small-tube writing instruments and the like, having a writing point at the front end thereof, an ink tank for directly storing ink and a collector or grooved adjuster for absorbing variation in internal pressure. In particular, the present invention relates to improvement of the mechanism to solve the flooding problem occurring when a collector type writing instrument is used under conditions in which a sharp pressure variation occurs such as on an airplane and its bad appearance when parts are incorporated in the ink tank.
Writing instruments which have a collector 6 as an internal pressure adjuster, disposed between a conventionally existing point assembly 1 and ink tank 3, for retaining free-state ink 2 and adjusting the pressure inside ink tank 3 so as to prevent ink leakage from a tip 9 of point assembly 1 and ink flooding from an air hole 10 have been known (see FIG. 5).
A collector type writing instrument can adjust the internal pressure balance by temporarily storing ink 2 of a relatively low viscosity from ink tank 3 within retaining grooves 13 formed in collector 6 or storing ink within fibers using capillarity, and returning ink to ink tank 3, meaning that it provides the function of protecting the writing point from the influence of changes in pressure.
A collector type writing instrument has excellent performance such as capabilities of providing an ample amount of ink, securing the stable amount of ink flow down to the last drop and allowing for the amount of ink 2 left to be checked from the outside.
However, since the collector type writing instruments store ink 2 directly and allow movement of ink 2 to and from collector 6, there is a serious drawback that ink 2 will flood outside through air hole 10 of the writing instrument there being no space for withholding ink 2, there by polluting fingers or clothes if the writing instrument is exposed to an environment in which the ink inside collector 6 exceeds the maximum capacity of retention, which is the limitation of the internal pressure adjustment capacity. As the countermeasures for solving this problem or increasing the safety to some degree, it is possible to make collector 6 greater in capacity or make ink tank 3 smaller. There have already been writing instruments sold on the market which use a collector capable of preventing ink flood under usual environments, meaning gentle temperature changes and the like.
As the current situation is that collector type writing instruments use rather thick barrels, taking a safety margin into account, use of a thicker barrel than the present situation makes the instrument difficult to grip and loses the stylishness.
When ink tank 3 is made smaller, reduction of ink stored makes the life short. In contrast, when the normal collector 6 is made longer, the ink head H becomes higher because the ink head H acting on point assembly 1 is proportional to the height from the air/liquid exchanger 18 to the tip 9 of the writing assembly, hence forward leakage of ink 2 from tip 9 occurs.
On the other hand, when a writing instrument which has been capped under about 1 atm. on the ground and is uncapped inside an airplane in which the air pressure is generally reduced to about 0.8 atm., the interior of the pen which has been balanced under 1 atm., is instantaneously exposed to an environment of about 0.8 atm., so ink 2 inside moves in a rush and floods the space around the air channel of collector 6, whereby ink 2 floods out from air hole 10, being unable to be properly retained by the whole part of retaining grooves 13.
In order to solve the flooding problem occurring under conditions in which the air pressure varies, devices and inventions have been disclosed in Japanese Utility Model Publication Hei 3 No. 31580, Japanese Utility Model Publication Hei 3 No. 31581 and Japanese Patent Application Laid-open Hei 9 No. 104194, and others.
However, these disclosures only provide the function of blocking the flush to directly reach the air hole, hence a further effective improvement or other ways to reach a solution have been demanded.
There has been an invention which uses an air supply pipe and the like as disclosed in Japanese Patent Application Laid-open Hei 4 No. 227886. However, the conventional invention has the problem that the instrument cannot write continuously unless the writing element is turned down-side up for ink supply and also has the problem of ink capacity being only half filled up from the beginning. Therefore, it is necessary to add such usage instructions or explanation as to the initially reduced amount of ink, for the consumers.
Since it is considered that the instrument may be used in an environment in which sharp increase and reduction in air pressure repeatedly occur as in the situations where the instrument is carried over from one airplane to another or from low temperature outdoor air to the front of a heater, there have been demands for excellent free-state ink collector type writing instruments which do not need any usage explanation to consumers as above, adopt effective countermeasures against such repeated changes and still can provide beneficial writing comfort making use of low-viscosity ink 2.
As ink 2 is consumed during writing, collector type writing instruments are adapted to take external air into the ink tank 3 side through air/liquid exchanger 18 so as to avoid reduction in internal pressure. Therefore, it is usually necessary to provide a space in the rear of collector 6 for allowing free movement of air bubbles.
As conventionally disclosed in Japanese Utility Model Application Laid-open Sho 59 No. 184682 and other publications, in a configuration in which a solid article such as an ink absorber etc., is arranged in the ink tank, in contact with the rear of the collector, if air bubbles arising at the air/liquid exchanger do not pass through the ink absorber, which is wetted with ink, without resistance, the ink absorber itself will function as a second air/liquid exchanger. In this case, the internal pressure inside the writing instrument lowers, causing ink starvation and other writing deficiencies.
To solve the above problem, it is necessary to provide an arrangement which will not confine the rear of the collector or any other countermeasure. However, the air/liquid exchanger in the collector is usually provided at a single site, meaning that the position of the air/liquid exchanger should be well adjusted to that of the air bubble passage of the ink absorber when assembled.
When a small-diametric ink absorber is used to be built in so as to allow ink to move in and out around it, it is effective in preventing flooding. Since the ink absorber is somehow narrowed, it is necessary to make the ink absorber longer to make up for this thinning down. However, when ink held in a transparent ink tank runs out, the interior can be seen, so that, if the aforementioned part remains wetted with ink, it can be misapprehended as if there were still ink left. There occurs such an appearance problem.
Accordingly, there is a demand for solution to these problems.
Further, since collector type writing instruments have the problem that the life of writing abruptly ends when ink runs out, it is necessary to carry a spare if the writing instrument has a low amount of ink. There is a demand for collector type writing instruments which can provide an ample amount of ink, which is the feature of collector type writing instruments, until nearly the end of writing and can provide the performance of a fabric sliver type instrument, which delivers gradually reducing amounts of ink, for a short time at the end of its writing life so that the pen can be used to take some notes after the last drop of ink is used up. There are also other problems, including the problem of ink dropping from the writing point making it difficult to write when the pen has been kept upside down for long time, and the problem of ink leaking forwards due to deficiency of the inherent function of a collector type writing instrument because ink drops and the air/liquid exchanger dries when the pen is held with its tip up and the air/liquid exchanger cannot be wetted again with ink even when the pen is returned with its tip down if there is a part in the way that blocks ink. Even when an equal amount of ink is loaded, a collector type writing instrument delivers a greater amount of ink than a conventional fabric sliver type writing instrument and hence has a shorter life. Therefore, downsizing of the ink tank volume should be avoided as far as possible. There are demands for solution to these problems.
It is therefore a main object of the present invention to provide improvement of collector type writing instruments of prevalent models. In detail it is an object to provide a writing instrument which, without the necessity of a special configuration limiting the usage, can avoid crucial accidents such as pollution of consumer""s clothes or fingers, due to forward leakage of ink 2 from tip 9 of point assembly 1 or flooding of ink 2 from air hole 10 exceeding the limit of the pressure adjustment capacity of collector 6, by absorbing the variation in pressure inside ink tank 3 resulting from change in temperature or air pressure.
There has been a demand for solution to the defect of collector type writing instruments, i.e., the liability to cause flooding especially when they are used on an airplane or under an environment in which sharp temperature change occurs. Therefore it is a first object of the present invention to provide an inexpensive collector type writing instrument with the above problem removed while the appearance and writing distance (life) are maintained as before.
Further, it is a second object of the present invention to provide a writing instrument which is able to secure flow channels that will not limit ink communication and passage of air bubbles when an ink absorber 31 and other parts are added as a means for solution of the above problem and which is free from the appearance problem of the amount of ink left being unable to be monitored because of the added parts, or which is configured so as not to receive any influence on the view of the amount of ink left.
It is also a third object of the present invention to prevent forward leakage by quickly wetting the air/liquid exchanger of writing instrument when it is used for writing in its downward position from a state where the air/liquid exchanger has been dried in its upward position.
It is possible to provide a further efficient writing instrument if the end of writing life problem and the ink drop problem can be solved.
In general, collector type writing instruments include ball-point pens, fountain pens, small-tube writing instruments and the like which have an ink feeder core (center core 8 and/or collector core 7) for assuring the flow path of ink 2 having a low viscosity (100 mPa.s or lower) from an ink tank 3 to a writing point 9 provided at the tip of a point assembly 1 or which have an ink feeder portion made up of a slit (in the case where a vertical groove 14 is extended to the tip) in a collector 6, 6a, and felt tip pens, markers and the like in which the ink feeder core (7, 8) itself serves as a writing tip 1. Hereinbelow, ink feeder cores (center core 8, collector core 7, etc.) will also include those which themselves serve as pen tips.
Arranged between ink tank 3 of a cup-like shape having a bottom integrally formed or assembled with a separate part such as a tail plug or the like and a point assembly is a collector 6, 6a, which may be formed of a plurality of retaining grooves 13 (generally, gaps defined by a plurality of vanes 12), an air groove 15 connected to the external air and a narrow longitudinal groove 14 creating communication between retaining grooves 13 or which may be made up of a fiber bundle, so as to retain ink 2 using capillary capacity. An air/liquid exchanger 18 of a small enough size is provided for collector 6, 6a and is adapted to be wetted with ink 2, so that ink tank 3 can be isolated from the external air and air will not enter ink tank 3 from the outside other than through air/liquid exchanger 18.
In the present invention, a collector writing instrument of an above-described general model is first provided with a snorkel 25, as an effective means of the present invention, which has a tubular vent portion 27, formed integrally or by assembly of parts, for releasing the air expanded in the rear part inside ink tank 3 to the collector 6, 6a side to thereby prevent application of pressure on ink 2. This arrangement functions as an effective means to prevent ink 2 from flooding when ink 2 has been consumed to some degree or the air inside ink tank 3 occupies the interior space to a certain degree in a state where point assembly 1 is placed downwards.
The snorkel 25 is also formed integrally or as a separate part, with a sectioning portion 26 for virtually separating ink tank 3, so that air can be easily ventilated through vent portion 27 of snorkel 25. An ink conduit 30 that is sized so as to be more unlikely to pass air than vent portion 27 does is formed as appropriate in sectioning portion 26.
In order for air bubbles, which are formed when air enters ink tank 3 through air/liquid exchanger 18 of collector 6, 6a from the outside during writing, to be able to move to the rear space without receiving significant friction from ink absorber 31 and snorkel 25 etc., a clearance portion 42 is preferably provided between the collector 6, 6a and snorkel 25. The clearance portion 42 also functions as an air channel for relieving the relatively high internal pressure in ink tank 3 of the writing instrument when the ambient environment of the writing instrument is relatively low in pressure.
The first effective means of the present invention is configured so that snorkel 25 is equivalent in wettability to collector 6, 6a. As the specific means, snorkel 25 is molded of the same material as the collector is, or is subjected to the same wettability reforming treatment as collector 6, 6a is, so that the snorkel is equivalent in wettability to collector 6, 6a. Usually, collector 6, 6a is molded of a material having resistance to ink such as ABS, AS, PS, PP, PET, or these resins kneaded with additives such as surfactants and the like. More generally, the collector may be subjected to a hydrophilic treatment utilizing a plasma treatment or achemical treatment with a mixture of sulfuric acid and chromic acid, aiming at improvement of ink wettability of surfaces. These techniques have been conventionally done. Since snorkel 25 of the present invention can also be improved in wettability to ink 2 by using a similar material or surface reforming treatment, air bubbles can readily move during writing hence the writing performance is unaffected while ink 2 spreads over the surfaces of the parts inside ink tank 3 in an extremely thin manner, whereby improvement against the appearance problem when no ink is left can be expected.
The second effective means of the present invention is configured so that snorkel 25 is equivalent in wettability to ink tank 3. As the specific means, snorkel 25 is molded of the same material as ink tank 3 is, or is subjected to the same wettability reforming treatment as ink tank 3 is, so that the snorkel is equivalent in wettability to ink tank 3. Usually, ink tank 3 is molded of a material having resistance to ink such as AS, PS, PP, PET, or these resins kneaded with additives such as Teflon particles and the like, aiming at lowering surface wettability so as to repel ink. Conventionally, oil-based ball-point pen tubes and the like have been molded of PP resin which is less wettable or have been subjected to a water-repellent treatment such as silicone oil coating or Teflon coating. Since snorkel 25 of the present invention can also be lowered in wettability to ink 2 by using a similar material or surface reforming treatment, air bubbles can readily move into vent portion 27 during writing hence the writing performance is unaffected while ink 2 is repelled by the parts inside ink tank 3, whereby improvement against the appearance problem when no ink is left can be expected.
As the third effective means of the present invention, an ink absorber 31 made up of a fabric sliver, sponge, fiber bundle, foamed material, or the like capable of retaining ink is incorporated in ink tank 3 and connected to center core 8, collector core 7 or longitudinal groove 14 for leading ink 2 from ink tank 3 to point assembly 1.
Ink absorber 31 is arranged so as to at least reach a position more rearward than the approximate center of ink tank 3 and so as to be able to absorb ink 2 through front and rear openings thereof.
As ink absorber 31, a fiber bundle core which is formed by bonding or forming ordinary fibers with adhesives or with heat, a fabric sliver made up of soft fibers or a continuous-foamed sponge, covered by an unabsorbent cladding can be used. In order to use ink 2 efficiently, necessary methods such as reducing the capillary capacity lower than that of center core 8 and collector core 7 may be preferably employed as appropriate.
As the fourth effective means of the present invention, a cladding 35 of ink absorber 31 is configured so as to be equivalent in wettability to ink tank 3 or snorkel 25. As the specific means, cladding 35 is molded of the same material as snorkel 25 or ink tank 3 or is subjected to the wettability reforming treatment as described above so that the cladding is equivalent in wettability to snorkel 25 or ink tank 3. This configuration eliminates the appearance problem relating to ink wettability.